(CNN) -You can't see, smell or taste radon gas, but the silent killer could be lurking in your home. Radon is actually the second leading cause of lung cancer in the U.S. and causes more than 21,000 lung cancer deaths per year.

The U.S. Environmental Protection Agency has declared January as National Radon Action Month in an effort to bring awareness to this naturally occurring radioactive gas. Because radon is a gas, it is everywhere.

"That is something that we can inhale. It can get stuck with dust and then we inhale the dust, and over a long time it can cause damage in ourselves, in the lungs and then eventually cause lung cancer," said Cleveland Clinic's Dr. Humberto Choi.

Dr. Choi says your basement is often the first place to look, as the gas released from the soil under your home can get trapped there. It's important to note that radon levels can vary from day to day and even change during different times of the day.

Testing for radon is relatively easy. Test kits can be purchased at most home improvement stores or online. Dr. Choi says radon exposure is more common than most people think. The EPA estimates that one in every 15 houses is exposed to a high level of radon. He says people who have been exposed to radon for long periods of time, who are also smokers, should be most concerned.

"Especially if you smoked in your life, the risk of having lung problems, especially lung cancer, can be higher than if you just smoked, or if you just had exposure to radon," Dr. Choi said.

The good news is that the problem can be fixed. If your home tests high for radon, the EPA recommends contacting a licensed professional to learn which radon reduction techniques are best for your home.

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